This application claims the priority of German patent application DE 196 47 305.5, the disclosure of which is expressly incorporated by reference herein.
The invention relates to an electromagnetic actuator for a charge change valve (poppet valve) for an internal combustion engine.
German patent document DE 43 36 287 C1 discloses a device for compensating for changes in length of the valve drive during operation. Clamping elements are used for this purpose. If clamping of the electromagnet (switch magnet) is triggered by the clamping elements when the valve is closed, the electromagnet (switch magnet) attracts accordingly by means of the armature. This ensures that the electromagnet (switch magnet) responsible for the closed position can be "adjusted," and that the armature always rests exactly on the surface or the pole area of the magnet body of the switch magnet.
The object of the present invention is to provide a device of this type which permits simple hydraulic length compensation in a valve drive during operation.
This object is achieved by the electromagnetic actuator according to the invention, which is float-mounted. This means that the complete actuator unit with the electromagnet, armature plate and other parts is mounted so that it can be displaced along the valve axis in the cylinder head. For this purpose, the actuator unit can consist of a preassembled component. By deliberately allowing an escape of the pressure medium (generally oil), all moving parts of the device are supplied with lubricating oil by means of a suitable channel guide.
The play-compensating piston compensates for both "positive" and "negative" valve play. "Negative" valve play means that the valve no longer closes properly. In this case, pressure medium is expelled from the second pressure chamber until the valve play is zero or until length compensation has been performed. Conversely, with "positive" play (play between the valve shaft and the actuating unit with the valve resting correctly on the valve seat), pressure medium is added to the first pressure chamber of the play-compensating piston until the play is again compensated, or until the valve shaft cooperates with the actuator unit with zero play.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.